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Basis for original (SCP) IDLH: The available toxicological data indicate that zirconium compounds possess a low order of toxicity. The chosen IDLH has been based on the citation by NIOSH [1976] that a 30-minute exposure to 500 mg/m3 of zirconium nitrate is the lowest concentration of this substance which has been shown to be lethal to rats [Mogilevskaya 1967].

Short-term exposure guidelines: None developed

ACUTE TOXICITY DATA:

Lethal concentration data:

Species

Reference

LC50

LCLo

Time

Adjusted 0.5-hr

LC (CF)

Derived value

Zr(NO3)2 Rat

Mogilevskaya 1967

-----

500 mg/m3

30 min

212 mg Zr/m3 (1.0)

21 mg Zr/m3

Lethal dose data:

Species

Reference

Route

LD50

(mg/kg)

LDLo

(mg/kg)

Adjusted LD

Derived value

ZrF6×2K Mouse

Shalganova 1967

oral

98

-----

221 mg Zr/m3

22 mg Zr/m3

Zr(SO4)2 Rat

Cochran et al. 1950

oral

3,500

-----

7,886 mg Zr/m3

789 mg Zr/m3

ZrOCl2 Mouse

Delongeas et al. 1983

oral

1,227

-----

4,398 mg Zr/m3

440 mg Zr/m3

ZrOCl2 Rat

Klimmer & Doll 1964

oral

2,950

-----

10,573 mg Zr/m3

1,057 mg Zr/m3

ZrCl4 Rat

ACGIH 1986

oral

1,688

-----

4,643 mg Zr/m3

464 mg Zr/m3

ZrCl4 Mouse

ACGIH 1986

oral

655

-----

1,801 mg Zr/m3

180 mg Zr/m3

ZrF4 Rat

ACGIH 1986

oral

98

-----

374 mg Zr/m3

37 mg Zr/m3

Human data: None relevant for use in determining the revised IDLH.

Revised IDLH: 25 mg Zr/m3

Basis for revised IDLH: The revised IDLH for zirconium compounds is 25 mg Zr/m3 based on acute toxicity data in animals [ACGIH 1986; Mogilevskaya 1967; Shalganova 1967]. This may be a conservative value due to the lack of relevant acute inhalation toxicity data for workers.